This application claims the priority of German Application No. 196 42 831.9, filed Oct. 17, 1996 and German Application No. 197 18 204.6, filed Apr. 30, 1997, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a method and an apparatus for applying self-adhesive protective sheeting to vehicle bodies.
In the mass production operation of many vehicle manufacturers, the vehicles have to be prepared for dispatch in such a way that they incur no damage, in particular in such a way that the paintwork is not adversely affected by storage and atmospheric influences. If rail travel or even transport by ship became necessary for transfer to the customer, the vehicles were covered for this purpose with a protective wax layer which had to be removed again before delivery to the customer. The complete removal of the protective wax was not only labour-intensive work, but also caused pollution for humans and for the environment on account of the solvents which were used at the same time.
There has therefore recently been a tendency to protect the bodies during transport by means of self-adhesive sheetings, although only the essentially horizontal surface parts of the body which are at risk from atmospheric influences and precipitation have been protected in this way. Since this type of protection is not only highly effective, but also relatively expensive, it was provided not only as protection during transport, but also as protection during vehicle assembly, and the protective sheeting was therefore applied even before the final assembly of the vehicle, that is to say immediately after the painting of the body. Such protection is advantageous not only for conventional saloon cars of hatchback design, but also for all possible vehicles, such as, for example, estate cars, small buses, so-called large-capacity saloons or cross-country vehicles.
The protective sheeting is to be applied so as to be as free of creases and bubbles as possible, because a microclimate may form under creases or bubbles after a certain amount of storage time, and this microclimate may, under some circumstances, lead to visible traces, depending on the type and colour of the paint. So that protective sheetings can be applied with great care, the sheeting blanks have hitherto had to be held by four persons, brought over the vehicle, aligned and laid onto the associated surface parts. Despite the large amount of manpower, it was not always possible to avoid creases or bubbles when the protective sheeting was being applied. When the regions for accessory parts were subsequently cut free, damage to the paintwork often occurred, so that complicated reworking became necessary.
The following procedure has hitherto been adopted for the manual application of the protective sheeting: in the first place, a rectangular piece of protective sheeting coordinated in terms of size with a surface part was drawn off by at least two persons from a stock roll and was cut off, and it had to be received by four persons altogether. This piece of protective sheeting was stretched out freely, with a self-adhesive side facing downwards, by the four persons with their bare hands, brought in this way over the body, lowered in the correct horizontal position onto the associated surface part, laid onto it so as to be more or less free of creases and bubbles and pressed down by brushing with a soft slideable article, for example a piece of stiffened felt. In the region of glued-over gaps with adjacent body parts, such as mudguards or doors, protective sheeting was cut through manually with a knife and the cut edges pressed down by hand.
So that the protective sheeting could be cut free and clearances made in it in a manner appropriate for assembly in the region of accessory parts, such as roof trim bars, sliding-roof covers, radiator cowlings, screen-washing nozzles, aerials, screen frames or the like, previously a flat strip-shaped stencil was applied to the body in the correct position during the manual application of the sheeting and the protective sheeting to be applied was likewise glued over the stencil, so that the sheeting was not only held at a short distance from the body surface on the regions to be cut free, but the stencil also formed a cutting and guiding edge for a knife, along which edge the sheeting could be severed in a manner appropriate to the contour. At the hectic pace adopted, despite constant practice, working with a sharp-edged knife very close to the painted body surface repeatedly resulted in paint damage and in complicated reworking.
This state of the art corresponds to manufacturing practice, at least where the applicant is concerned; since, for reasons of environmental protection, the USA no longer allows protective waxings in vehicle dispatch, it is likely that other vehicle manufacturers too have also changed to a similar protective sheeting system for their vehicles during dispatch. However, the applicant does not know of any publication relating to this.
Proceeding from this state of the art, the object of the invention is to improve the application method and the corresponding apparatus to the effect that monotonous manual work can be replaced by mechanization, the quality of application as regards the freedom of the applied protective sheeting from bubbles and creases as well as the avoidance of paint damage can be improved, and, moreover, labour costs can be saved.
According to the invention, this object is achieved by mechanizing the application of sheeting to the body. A specific rectangular piece of a protective sheeting from a stock roll is grasped on the non-adhesive side by using a robot-controlled tentering frame, preferably with suction legs. The piece is drawn off from the stock roll and is cut off. Before the sheeting blank is laid onto the body, perforated tear-off lines are made in the region of accessory parts by means of a perforating tool while the sheeting blank is in the freely stretched-out state. (For example, the protective sheeting is perforated from its non-adhesive side by means of a heated serrated disk guided mechanically along defined contour lines.) Thereafter, the protective sheeting, thus prepared, is stretched out so as to be free of creases in the tentering frame, lowered in the correct position onto the associated surface part by the handling robot, laid on so as to be free of bubbles and pressed down by means of a brushing bar. All the surface parts are thereby glued over in succession. In the region of accessory parts, protective sheeting parts are drawn off along the perforated tearing lines and clearances are thus made in the regions in a manner appropriate for assembly.
In an expedient embodiment of the invention, the initially loosely applied sheetings are all pressed down jointly. In the region of glued-over gaps, the protective sheeting is severed and the cut edges are expediently pressed down by means of a rotating brush in the gap region.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.